Landslide leaves engineers to ponder options for Highway 1

Bret Haney, construction inspector with Caltrans, looks at the south side of a landslide on Wednesday, May 24, 2017, after a massive slide went into the Pacific Ocean over the weekend in Big Sur, Calif. The slide buried a portion of Highway 1 under a 40-foot layer of rock and dirt and changed the coastline below to include what now looks like a rounded skirt hem, Susana Cruz, a spokeswoman with the California Department of Transportation, said Tuesday. (Joe Johnston/The Tribune (of San Luis Obispo) via AP)

Photo: Joe Johnston, Associated Press

The massive landslide that swallowed a stretch of Highway 1 on the Big Sur coast over the weekend was still spewing rock and dirt down a remote mountainside Thursday, and state officials say it will probably be next year before they get the wall of mud out of the way.

The continued movement of the quarter-mile-long slide near the Monterey County community of Gorda has kept Caltrans engineers from taking stock of the situation and figuring out when — and if — the section of road that serves as the southern gateway to Big Sur can be repaired and re-opened.

Independent experts say the solution may require constructing a sprawling bridge over the troublesome spot or a tunnel deep in the ground beneath it, a prospect that could take years and cost the state hundreds of millions of dollars.

“This one is quite a hurdle,” said Robb Moss, a professor of civil engineering at Cal Poly San Luis Obispo. “It exceeds a lot of the usual fixes.”

Saturday’s slide in the sparsely populated Mud Creek area is believed to have been caused by groundwater that has continued to percolate up and out of the mountains, months after the winter’s near-record rains. As the steep cliffs above the ocean became saturated, they collapsed under their own weight across the highway and into the ocean — where a peninsula of rock and mud has emerged.

Moss said the best-case scenario for getting the road open would be putting in a stretch of asphalt, at least temporarily, on top of the slide once the area dries out come summer. That option, though, is contingent on soil tests to determine whether the mountainside is secure.

“Hopefully, this season you can get in a couple of lanes,” he said. “But if it’s not remaining stable in the long term, you have to look at a more expensive fix.”

Landslide leaves engineers to ponder options for Highway 1

1of2In this aerial photo taken Monday, May 22, 2017 provided by John Madonna showing a massive landslide along California's coastal Highway 1 that has buried the road under a 40-foot layer of rock and dirt. A swath of the hillside gave way in an area called Mud Creek on Saturday, May 20, covering about one-third of a mile, half a kilometer, of road and changing the Big Sur coastline. (John Madonna via AP)Photo: John Madonna, Associated Press

2of2Waves crash on the shore on Wednesday, May 24, 2017, after a massive landslide that went into the Pacific Ocean over the weekend in Big Sur, Calif. The slide buried a portion of Highway 1 under a 40-foot layer of rock and dirt and changed the coastline below to include what now looks like a rounded skirt hem, Susana Cruz, a spokeswoman with the California Department of Transportation, said Tuesday. (Joe Johnston/The Tribune (of San Luis Obispo) via AP)Photo: Joe Johnston, Associated Press

Stretches of Highway 1 have been washed out in the past, and a number of techniques have been used afterward. The simplest has been building a new road, which can be accomplished only when the ground, or at least the underlying rock, is strong enough to anchor new pavement. To guard against future landslides, nets, retaining walls or rock sheds, which offer overhead protection, have been installed.

Pricier fixes include viaducts that bypass the problem areas as well as tunneling into and below a landslide. Many have called for such big-ticket repairs at Mud Creek for decades and Moss and others say it may finally be time.

Some are likening the situation to Devil’s Slide in San Mateo County, where Caltrans went for years trying to clear the highway of wintertime debris before turning to two 4,200-feet long tunnels at a cost of more than $400 million.

“Long term, it may be the solution,” Moss said.

Caltrans officials won’t have a repair plan until they’re able to drill beneath the slide and evaluate the ground below. But they say they’re certain they’ll find a way — eventually — to reopen the area for travel.

“The Big Sur highway is a worldwide destination for people,” said Caltrans spokesman Jim Shivers. “We won’t walk away from Big Sur no more than we walk away from highways that run through Yosemite or Lake Tahoe or any area that could be impacted by weather.”

The transportation agency has racked up what may be a record backlog of roadwork because of storm damage across California.

Even before Saturday’s slide, an estimated $1 billion was needed for state highways fixes, Caltrans officials said, more than double the $383 million average annual repair bill from the previous five years. The high price is the result of an historically wet year that has left roads washed out from the Santa Cruz Mountains to the Sierra.

But nowhere has the damage been more severe than Big Sur. A condemned bridge over Pfeiffer Canyon, which has prompted a second closure of Highway 1 north of the recent slide, is expected to cost $26.5 million to replace. Several other landslides along the highway around Big Sur will cost millions more to clear.

At Mud Creek, the million-plus tons of debris that fell from the mountain is actually the result of four previous slides, each earning names from the locals over the years. Last weekend, they came together as one in an avalanche unlike any since the early ’80s.

Highway 1 in the area was closed at the time because of previous slides, and no one was injured.

“It’s some of the steepest, highest terrain closest to the ocean on the West Coast,” said Gary Griggs, a professor of earth sciences at UC Santa Cruz. “You can’t prevent these things from happening. The scale is too big. It’s just what we’ve got to live with here. It’s what Mother Nature gave us.”

Big Sur is open for business. But with this year’s big winter storms continuing to wreak havoc on roads and trails, getting to one of California’s most dramatic stretches of coastline isn’t easy — and it can also be very expensive.

Here are some options for people determined to have a Big Sur Memorial Day weekend:

Helicopter:It offers the shortest route in. The luxury Post Ranch Inn, which is among many destinations on the southern end of Big Sur that can’t be accessed because of mudslides, is promoting a two-night stay that includes a flight in and out, starting at $4,291. The ride takes 15 minutes from the Monterey Peninsula.

Driving in from the north:Rest assured the northern half of Big Sur along Highway 1 is wide open. Tourists are free to drive in through Monterey and Carmel, enjoying such coastal sites as Garrapata State Park and parts of Pfeiffer Big Sur State Park along the way.

Be warned, though, that many inland portions of the parks remain closed because of burn damage from last year’s Soberanes Fire. Several places are off-limits because of winter storm damage.

Where things get tricky is just south of Pfeiffer Big Sur State Park at Highway 1’s Pfeiffer Canyon Bridge. The road stops because of bridge damage and isn’t expected to be fixed until the end of September.

Driving in from the south:Much of Highway 1 in the southern part of Big Sur remains closed, and driving in from San Luis Obispo County won’t be possible for months. However, for those with time — and good tires on their car — narrow Nacimiento-Fergusson Road allows visitors to approach from the east, off Highway 101. The long, winding drive brings travelers to Highway 1 near Lucia, where a 10-mile stretch of Highway 1 in Big Sur is open.

The 10-mile stretch is a rural area that includes Limekiln State Park, which is open.

Kurtis Alexander is a general assignment reporter for The San Francisco Chronicle, frequently writing about water, wildfire, climate and the American West. His recent work has focused on the impacts of drought, the widening rural-urban divide and state and federal environmental policy.

Before joining the Chronicle, Alexander worked as a freelance writer and as a staff reporter for several media organizations, including The Fresno Bee and Bay Area News Group, writing about government, politics and the environment.